The present invention relates to a method and apparatus for handling cartons, especially cartons of the type in which lettuce is packed for shipment to the market. Lettuce is harvested in the field and packed into cartons for transport to a cooling and shipping location. Since lettuce heads are of various sizes and the cartons are preferably packed with the same number of heads, frequently the tops and/or bottoms of the cartons bulge. The bulging causes instability when the cartons are stacked thereby making difficult the transportation from the field on the field trucks and the subsequent loading in transport vehicles for shipment to the market.
In the field the lettuce cartons are usually stacked on pallets carried by field trucks for transportation to the cooling and loading location. Cooling is accomplished by drawing a vacuum on the lettuce which causes rapid evaporation and the resultant lower head temperatures. A lift truck is used to shift the loaded pallets from the field truck onto a transport mechanism which carries the pallets through the cooler. Thereafter the cartons must be moved to the transport vehicles which in the usual case are trailer trucks.
Prior to loading onto the transport vehicles the pallets must be removed for re-use thereby making it necessary that the cartons be loaded without pallets. The truck trailers are of various widths usually ranging between 88 and 91 inches or 2.33 to 2.31 meters wide. In the past the cartons have usually been transported to the vehicles in single file on conveyors and hand stacked in the vehicles, a time-consuming, expensive and difficult procedure.
The overall purpose of the present invention is provide a system for handling cartons in a manner to make use of mechanical devices for unitized loading and such that the cartons are efficiently loaded and closely positioned to limit damage during shipment.